Hunter Pro-C Installation Directions Confusing

The directions appear to say that I CANNOT expand from 3 stations to 12 stations by using a PCM-900 module to add 9 additional stations. They say that the PCM-900 module MUST BE USED ALONG WITH one PCM-300 module (in addition to the 3 stations that come with the controller) to expand to a total of 15 stations. I don't need 15 stations. Please confirm whether or not I can simply add the PCM-900 module to the 3 stations that come from the factory. Thank you.

Thanks for your response. It seems like you should be able to do that, but it is a moot point now as I have returned the 9-station module after talking with Sprinkler Warehouse, who said that it is NOT possible to simply add the 9-station to the base 3-station controller. I was advised to add three 3-station modules to get my 12, so I am moving in that direction.